What Is 7075 Aluminum?
7075 aluminum is a type of aluminum alloy.
The main component is aluminum, to which are added 1.2 to 2.0% copper, 2.1 to 2.9% magnesium, and 5.1 to 6.1% zinc. It has the same strength as steel, but is lighter.
Compared to duralumin, it is about 1.5 times stronger. However, its high copper content makes it less resistant to corrosion, which is a disadvantage. Care should be taken because its strength decreases after a long period.
Uses of 7075 Aluminum
7075 aluminum is light for its strength, about one-third lighter than stainless steel, which is a common steel material. Taking advantage of this feature, it is used not only for various aircraft materials but also for baseball bats. Besides railroad cars, it can be used for various sporting goods, such as metal bats, ski boards, and stocks.
However, 7075 aluminum has low corrosion resistance. Therefore, when used where corrosion resistance is required, it is sandwiched between materials with superior corrosion resistance, such as stainless steel. Rivet bolts are also used for welding to increase the degree of fixation.
Types of 7075 Aluminum
7075 aluminum is a type of duralumin included in aluminum alloys. There are three types of duralumin: duralumin, 7075 aluminum, and super duralumin.
Duralumin and super duralumin are mainly alloys of aluminum and copper. In contrast, 7075 aluminum is an alloy of copper, zinc, and magnesium with aluminum as the main constituent.
The hardness of duralumin can be compared to HB (Brinell hardness). Aluminum is 65 HB, duralumin is 105 HB, 7075 aluminum is 120 HB, 7075 aluminum is 160 HB, and stainless steel is 187 HB.
Principle of 7075 Aluminum
In 1906, an aluminum alloy with copper added was produced. Especially when left for a day, it shows a significant increase in hardness compared to that immediately after quenching. This aluminum alloy entered the market as duralumin.
Duralumin with high tensile strength was developed in 1928. In 1931, an alloy without silicon and with an increased magnesium content of 1.5% was invented.
Stress corrosion cracking, however, was a problem with many high-strength metals. To prevent stress corrosion cracking, it was counteracted by the addition of chromium. In 1936, 7075 aluminum, the strongest duralumin at that time, was developed.
How to Select 7075 Aluminum
1. 7075 Aluminum
7075 aluminum is one of the strongest aluminum alloys. The proportion of magnesium is increased and zinc is added for strength. The higher the “super” in duralumin, the higher the strength, but the weight, weldability, and corrosion resistance of the alloy itself remain almost the same.
2. Duralumin
Common duralumin is the least expensive of the three types of duralumin. It is used in familiar products, of which duralumin cases are a typical example. It is lightweight, strong, and suitable for carrying luggage.
3. Super Duralumin
7075 aluminum is an intermediate strength between 7075 aluminum and 7075 aluminum super-duralumin. Like 7075 aluminum, it is often used for aircraft parts.
Structure of 7075 Aluminum
To ensure strength, magnesium, copper, and zinc are added to aluminum in 7075 aluminum. The addition of zinc increases strength but creates a small risk of stress corrosion cracking.
Duralumin is a material whose strength is increased by age hardening. Age hardening is a phenomenon in which, after quenching, the material is left to rest for a day or so and its strength is higher than that of the material immediately after quenching. Although Duralumin is made stronger by age hardening, it loses its strength little by little when used over a long period.